Piezo-electric actuators

ABSTRACT

There is provided a piezo-electric actuator comprising an assembly comprising a first electrode, a second electrode, and at least one piezoelectric layer located between said first electrode and said second electrode, wherein at least one of the first electrode and the second electrode is split into at least two different sub-electrodes, wherein at least part of the assembly is configured to move along an axis perpendicular to a surface of the assembly, in response to an electrical stimulus applied to at least one of said first and second electrodes.

TECHNOLOGICAL FIELD

The presently disclosed subject matter relates to piezoelectric elementsin general, and specifically to sound pressure producing elements whichcomprise piezoelectric elements and which can be used in Digital SoundReconstruction (DSR) speakers.

BACKGROUND

DSR speakers can use different types of actuation, such aselectromagnetic actuation, electrostatic actuation, or piezoelectricactuation.

For example, DSR speakers are disclosed in U.S. Pat. Nos. 8,085,964,8,780,673 and U.S. Patent Publication Number 2015/0071467, to the sameApplicant.

Piezoelectric actuators are also known in the art, such as PI CeramicsGMBH PL022.30 or PL112-PL140.

Acknowledgement of the above references and device herein is not to beinferred as meaning that these are in any way relevant to thepatentability of the presently disclosed subject matter.

DSR speakers are speakers that generally use an array of small movingelements, as opposed to a single large membrane, to create audiblesound. Each one of these small moving elements is capable of producingsound pressure wave pulses. An original sound waveform can bereconstructed by DSR speakers when the number of pulses-per-clockcorrelates to the sound pressure wave that one wants to produce and whenthe pulse clock frequency is higher than the human ear's capability ofdistinguishing the single pulses.

There is a need in the art for new DSR speakers and new methods ofmanufacturing said DSR speakers.

SUMMARY OF THE INVENTION

In accordance with certain aspects of the presently disclosed subjectmatter, there is provided a piezo-electric actuator comprising anassembly comprising a first electrode, a second electrode, and at leastone piezoelectric layer located between said first electrode and saidsecond electrode, wherein at least one of the first electrode and thesecond electrode is split into at least two different sub-electrodes,and wherein at least part of the assembly is configured to move upwardsor downwards, in response to an electrical stimulus applied to at leastone of said first and second electrodes.

According to some embodiments, both the first electrode and the secondelectrode are split into at least two different sub-electrodes.

According to some embodiments, a cross-section of the assembly has atleast one straight side.

According to some embodiments, the piezo-electric actuator furthercomprises a base, said assembly being secured to said base along atleast part of one side of said assembly.

According to some embodiments, the assembly is configured to bend alongan axis perpendicular to a surface of the assembly.

According to some embodiments, when a sub-electrode of the firstelectrode is connected to a positive potential, and anothersub-electrode of the first electrode is connected to a negativepotential, corresponding opposite sub-electrodes of the second electrodeare connected to opposite potentials with respect to the sub-electrodesof the first electrode.

According to some embodiments, the first electrode is connected to afirst conductive element, the second electrode is connected to a secondconductive element, wherein the first conductive element is not inalignment with the second conductive element.

According to some embodiments, for at least one of the first and thesecond electrodes, the two sub-electrodes are connected to an electricalsupply, wherein the two sub-electrodes comprise a first sub-electrodeand a second sub-electrode, wherein the second sub-electrode is locatedfarther from the electrical supply than the first sub-electrode, whereinthe piezo-electric actuator comprises a conductive layer connecting theelectrical supply to the second sub-electrode.

According to some embodiments, the conductive layer is insulated fromthe first sub-electrode by an insulating layer.

According to some embodiments, the conductive layer is electricallyconnected to the second sub-electrode through a via hole present in theinsulating layer.

According to some embodiments, for at least one of the first and thesecond electrodes, the two sub-electrodes are connected to an electricalsupply, wherein the two sub-electrodes comprise a first sub-electrodeand a second sub-electrode, wherein the second sub-electrode is locatedfarther from the electrical supply than the first electrode, wherein thepiezo-electric actuator comprises a metal trace adjacent to the firstsub-electrode connecting the electrical supply to the secondsub-electrode.

According to some embodiments, the piezo-electric actuator comprises athird electrode layer, a first piezoelectric layer located between saidfirst electrode and said third electrode, and a second piezoelectriclayer located between said third electrode and said second electrode.

According to some embodiments, said first and second electrodes includeconductive elements for at least one of the connection between differentelectrodes, the connection with another piezo-electric actuator, and theconnection with an external electrical supply.

According to some embodiments, there is provided an array ofpiezo-electric actuators comprising a plurality of piezo-electricactuators.

In accordance with some aspects of the presently disclosed subjectmatter, there is provided a method of controlling a piezo-electricactuator comprising an assembly comprising a first electrode a secondelectrode, and at least one piezoelectric layer located between saidfirst electrode and said second electrode, wherein the first electrodeis split into at least two different sub-electrodes, the methodcomprising feeding a sub-electrode of the first electrode with apositive electrical potential, and another sub-electrode of the firstelectrode with a negative electrical potential, in order to make theassembly bend upwards or downwards.

According to some embodiments, the assembly comprises a third electrodelayer, a first piezoelectric layer located between said first electrodeand said third electrode, and a second piezoelectric layer locatedbetween said third electrode and said second electrode.

According to some embodiments, the second electrode is split into twosub-electrodes, the method comprising feeding a sub-electrode of thefirst electrode with a positive electrical potential, and anothersub-electrode of the first electrode with a negative electricalpotential, and feeding corresponding opposite sub-electrodes of thesecond electrode with opposite electrical potentials with respect to thesub-electrodes of the first electrode.

According to some embodiments, for at least one of the first and thesecond electrodes, the two sub-electrodes are connected to an electricalsupply, wherein the two sub-electrodes comprise a first sub-electrodeand a second sub-electrode, wherein the second sub-electrode is locatedfarther from the electrical supply than the first electrode, the methodcomprising feeding an electrical potential from the electrical supply tothe second sub-electrode through a metal trace adjacent to the firstsub-electrode.

According to some embodiments, for at least one of the first and thesecond electrodes, the two sub-electrodes are connected to an electricalsupply, wherein the two sub-electrodes comprise a first sub-electrodeand a second sub-electrode, wherein the second sub-electrode is locatedfarther from the electrical supply than the first electrode, the methodcomprising feeding an electrical potential from the electrical supply tothe second sub-electrode through a conductive layer.

According to some embodiments, the conductive layer is electricallyinsulated from the first sub-electrode by an insulating layer.

In accordance with some aspects of the presently disclosed subjectmatter, there is provided a DSR speaker element comprising at least acentral moving element; a plurality of peripheral flexure benders, eachflexure bender comprising at least a pair of electrodes and at least apiezoelectric material layer, the flexure benders being connected tosaid moving element and being configured to move said moving elementalong an axis perpendicular to a moving element surface, in response toan electrical stimulus applied to said electrodes, in order to producesound, and at least a mechanical stopper which is configured to limitthe motion of said moving element.

According to some embodiments, the DSR speaker element comprises asubstrate comprising a cavity, said substrate also serving as saidmechanical stopper. According to some embodiments, the mechanicalstopper is located on one side of the moving element, wherein the DSRspeaker element further comprises an additional mechanical stopperlocated on the other side of the moving element. According to someembodiments, each flexure bender comprises a first electrode layercomprising a first electrode, a first piezoelectric material layer on atleast said first electrode layer, a second electrode layer on said firstpiezoelectric material layer, said second electrode layer comprising asecond electrode, and a second piezoelectric material layer on at leastsaid second electrode layer. According to some embodiments, each flexurebender further comprises a third electrode layer on said secondpiezoelectric material layer, said third electrode layer comprising athird electrode. According to some embodiments, the moving elementcomprises piezoelectric material and/or silicon or other material.According to some embodiments, at least part of any of said electrodesis split into at least two different sub-electrodes. According to someembodiments, a conductive layer and an insulating layer are disposed ontop of the sacrificial layer and below the first electrode layer.According to some embodiments, a conductive layer and an insulatinglayer are disposed on top of the top electrode layer. According to someembodiments, at least part of the piezoelectric material layer islocated between said pair of electrodes. According to some embodiments,the moving element and said piezoelectric material layer in each flexurebender are made by the deposition of a common piezoelectric materiallayer and the subsequent forming of gaps in said common piezoelectricmaterial layer. According to some embodiments, said gaps are formedsubsequently by the removal of fins made from a material which can beselectively removed, or the etching of the material in the gaps.According to some embodiments, for each flexure bender, a firstelectrode of said pair of electrodes is connected to a first conductiveelement, the first electrode and the first conductive element belongingto a first electrode layer, a second electrode of said pair ofelectrodes is connected to a second conductive element, the secondelectrode and the second conductive element belonging to a secondelectrode layer, and the first conductive element of the first electrodelayer is not in alignment with the second conductive element of thesecond electrode layer.

In accordance with some aspects of the presently disclosed subjectmatter, there is provided a DSR speaker comprising an array of DSRspeaker elements.

In accordance with some aspects of the presently disclosed subjectmatter, there is provided a method of forming a DSR speaker element, themethod comprising providing a substrate base; disposing a sacrificiallayer on at least part of said substrate base; disposing a firstelectrode layer on at least part of said sacrificial layer; disposing afirst piezoelectric material layer on said first electrode layer and onat least part of the sacrificial layer, disposing a second electrodelayer on least part of said first piezoelectric material layer, whereinat least part of the first and the second electrode layers are inalignment, forming gaps in the first piezoelectric material layer, todefine at least one peripheral flexure bender comprising a portion ofsaid first electrode layer, a portion of said first piezoelectricmaterial layer and a portion of said second electrode layer, and acentral moving element comprising another portion of said firstpiezoelectric material layer, wherein said flexure bender is connectedto said moving element, for moving said moving element in response to anelectrical stimulus applied to said first and second electrode layers.

According to some embodiments, at least part of the first and secondelectrode layers are deposited so as to have a curved shape. Accordingto some embodiments, the first and second electrode layers are disposedso as to each comprise a plurality of distinct electrode portions, themethod comprising forming said gaps in the first piezoelectric materiallayer, to define a plurality of peripheral flexure benders eachcomprising an electrode portion of the first electrode layer, a portionof said first piezoelectric material layer and an electrode portion ofthe second electrode layer, and a central moving element comprisinganother portion of said first piezoelectric material layer. According tosome embodiments, the method comprises disposing a second piezoelectricmaterial layer on at least part of said second electrode layer and on atleast part of the first piezoelectric layer located on the sacrificiallayer, and forming gaps in the first and second piezoelectric materiallayers to define at least one peripheral flexure bender comprising aportion of said first electrode layer, a portion of said firstpiezoelectric material layer, a portion of said second electrode layer,and a portion of said second piezoelectric material layer, and a movingelement comprising another portion of said first piezoelectric materiallayer and another portion of said second piezoelectric material layer,and disposing a third electrode layer on said second piezoelectricmaterial layer. According to some embodiments, the method comprisesremoving a portion of said substrate base at a diameter smaller than thediameter of said moving element, to form a cavity, and removing part ofthe sacrificial layer to form a mechanical stopper that limits themovement of said moving element. According to some embodiments, themethod comprises disposing a mechanical stopper on a side of said movingelement which is opposite to the substrate base, to limit the motion ofsaid moving element. According to some embodiments, the method comprisesafter the step of disposing a sacrificial layer on said substrate baseand before the step of disposing a first electrode layer on saidsacrificial layer, the step of disposing removable fins on saidsacrificial layer, said removable fins comprising a material that canlater be selectively removed for forming said gaps. According to someembodiments, the step of disposing a first piezoelectric material layercomprises one of the methods from the list of sputtering; sol-getdeposition; pressing a fine powder of piezoelectric material; andpressing a powder of piezoelectric material mixed with a binder.According to some embodiments, said step of forming gaps through saidfirst piezoelectric material layer comprises one of the methods selectedfrom the list of: a dry etching process; wet etching process, chemicaldissolving, and laser cutting. According to some embodiments, said firstand second electrode layers include conductive elements for theconnection between different electrodes of each electrode layer and forthe connection with another DSR speaker element and/or with an externalpower source. According to some embodiments, said first and secondelectrode layers include conductive elements which are not in alignment.According to some embodiments, the ratio of thickness of said flexurebender to the width of at least a gap of said gaps is larger than 2.

In accordance with some aspects of the presently disclosed subjectmatter, there is provided an array of DSR speaker elements formed usingsaid method of forming a DSR speaker element.

In accordance with some aspects of the presently disclosed subjectmatter, there is provided a method of forming a DSR speaker element, themethod comprising providing a substrate base; disposing a sacrificiallayer on said substrate base; disposing a first electrode layer on saidsacrificial layer; disposing a first piezoelectric material layer on atleast part of said first electrode layer, disposing a second electrodelayer on said first piezoelectric material layer, wherein at least partof the first and the second electrode layers are in alignment, disposinga moving element layer comprising a material different from apiezoelectric material; forming gaps on each side of a sectioncomprising a portion of the first electrode layer, a portion of thefirst piezoelectric material layer and a portion of the second electrodelayer, to define at least one peripheral flexure bender comprising saidportion of said first electrode layer, said portion of the firstpiezoelectric material layer and said portion of the second electrodelayer, and a central moving element comprising a material different froma piezoelectric material, wherein said flexure bender is connected tosaid moving element, for moving said moving element in response to anelectrical stimulus applied to said first and second electrode layers.

According to some embodiments, the first and second electrode layers aredisposed so as to each comprise a plurality of distinct electrodeportions, the method comprising forming said gaps, to define a pluralityof peripheral flexure benders each comprising an electrode portion ofthe first electrode layer, a portion of said first piezoelectricmaterial layer and an electrode portion of the second electrode layer,and a central moving element comprising a material different from apiezoelectric material.

According to some embodiments, the method comprises disposing a secondpiezoelectric material layer on at least part of said second electrodelayer and on at least part of the first piezoelectric layer located onthe sacrificial layer, and forming gaps on each side of a sectioncomprising a portion of the first electrode layer, a portion of thefirst piezoelectric material layer, a portion of the second electrodelayer, and a portion of the second piezoelectric material layer todefine at least one peripheral flexure bender comprising said portion ofthe first electrode layer, said portion of the first piezoelectricmaterial layer, said portion of the second electrode layer, and saidportion of the second piezoelectric material layer, and a central movingelement comprising a material different from a piezoelectric material,and disposing a third electrode layer on said second piezoelectricmaterial layer.

In accordance with another aspect of the invention a method of forming aDSR speaker element is provided. The method includes the procedures of:providing a substrate base, disposing a sacrificial layer on thesubstrate base, disposing a first electrode layer on the sacrificiallayer, and disposing a first piezoelectric material layer on the firstelectrode layer. The first piezoelectric material layer has a thicknessin the range of 1 μm-25 μm. The method also includes the procedure ofdisposing a second electrode layer on the first piezoelectric materiallayer in alignment with the first electrode layer. The second electrodelayer is shaped in the form of a flexure bender. The method alsoincludes the procedure of disposing a second piezoelectric materiallayer on the second electrode layer. The second piezoelectric materiallayer has a thickness in the range of 1 μm-25 μm. The method alsoincludes the procedure of disposing a third electrode layer on thesecond piezoelectric material layer in alignment with the firstelectrode layer and the second electrode layer. The third electrodelayer is shaped in the form of a flexure bender. The method alsoincludes the procedure of forming gaps through the first piezoelectricmaterial layer and the second piezoelectric material layer to define atleast one flexure bender attached to and located between a movingelement and an area surrounding the moving element. The flexure benderincludes the first electrode layer, the second electrode layer, and thethird electrode layer. The flexure bender also includes a portion of thefirst piezoelectric material layer sandwiched between the firstelectrode layer and the second electrode layer, and a portion of thesecond electrode layer sandwiched between the second electrode layer andthe third electrode layer, thereby forming a gapped depositedpiezoelectric layer including a flexure bender section and a movingelement section. The flexure bender section being connected to themoving element section and configured to bend and move the movingelement along an axis perpendicular to a plane of the surrounding areain response to an electrical stimulus to the electrode layers, andwherein the piezoelectric material in the moving element and theportions of piezoelectric material in the flexure bender are made from agiven piezoelectric material layer by the common deposition of thepiezoelectric material layers and the subsequent forming of gaps in thepiezoelectric material layers. The method also includes the procedure ofremoving a portion of the substrate base at a first diameter smallerthan the diameter of the moving element, thereby constituting a partialsubstrate base, to form a cavity and gain access to the sacrificiallayer element and forming a mechanical stop that limits the movement ofthe moving element. The method also includes the procedure of removing aportion of the sacrificial layer at a second diameter larger than thefirst diameter to form a space between a first side of the movingelement portion and the substrate base undercutting the firstpiezoelectric material layer and the second piezoelectric material layerand releasing an area below the flexure bender to allow free movement ofthe moving element.

In accordance with certain embodiments of the method of forming a DSRspeaker element the procedure of disposing a third electrode layer onthe second piezoelectric material layer is done after the procedure offorming gaps through the first piezoelectric material layer and thesecond piezoelectric material layer.

In accordance with certain embodiments of the method of forming a DSRspeaker element, the substrate base is made from one of the followingmaterials: glass and silicon.

In accordance with certain embodiments of the method of forming a DSRspeaker element the sacrificial layer is made from one of the followingmaterials: silicon dioxide and silicon.

In accordance with certain embodiments of the method of forming a DSRspeaker element the piezoelectric layer is made of PZT. In accordancewith other embodiments of the method of forming a DSR speaker elementthe piezoelectric layer is made of ZnO.

In accordance with certain embodiments of the method of forming a DSRspeaker element after the procedure of disposing a sacrificial layer onthe substrate base and before the procedure of disposing a firstelectrode layer on the sacrificial layer there is a procedure ofdisposing removable fins made from a material that can later beselectively removed on the sacrificial layer. The fins defining futuregaps in piezoelectric material that will be added later. These gapsdefine the flexure benders and moving element by separating them fromthe rest of the layer.

In accordance with certain embodiments of the method of forming a DSRspeaker element the procedure of forming gaps through the piezoelectricmaterial layer further includes the sub-procedure of removing fins.

In accordance with certain embodiments of the method of forming a DSRspeaker element the method includes the procedure of disposing a stopperon another side of the moving element to limit the motion of the movingelement when the flexure benders are actuated. The actuation is done byproviding electrical stimulation to the piezoelectric material layer viathe electrode layers.

In accordance with certain embodiments of the method of forming a DSRspeaker element, the procedure of disposing a first piezoelectricmaterial layer, and/or the procedure of disposing a second piezoelectricmaterial layer, comprises one of the sub-procedures selected from thelist of: sputtering, sol-get deposition, pressing a fine powder ofpiezoelectric material, and pressing a fine powder of piezoelectricmaterial mixed with a binder.

In accordance with certain embodiments of the method of forming a DSRspeaker element the procedure of forming gaps through the piezoelectricmaterial layer, and/or the procedure of removing a portion/section ofthe substrate base, and/or the procedure of removing a portion/sectionof the sacrificial layer, further comprises one of the sub-proceduresselected from the list of: a dry etching process, a wet etching process,chemical dissolving, and laser cutting.

In accordance with certain embodiments of the method of forming a DSRspeaker element, the electrode layers include conductive elements toconnect one electrode to the other electrode on the same electrodelayer, electrodes on one speaker element to electrodes on anotherspeaker element or to a power source.

In accordance with certain embodiments of the method of forming a DSRspeaker element, the conductive elements on the different electrodelayers are configured so as to have minimum capacitance between them.

In accordance with certain embodiments of the method of forming a DSRspeaker element, an array of DSR speaker elements formed using themethod is provided.

In accordance with certain embodiments of the method of forming a DSRspeaker element, a DSR speaker formed using arrays of DSR speakerelements formed using the method is provided.

In accordance with certain embodiments of the method of forming a DSRspeaker element, the procedure of disposing a first piezoelectricmaterial layer is followed by the procedure of sintering the firstpiezoelectric material layer.

In accordance with certain embodiments of the method of forming a DSRspeaker element the procedure of disposing a second piezoelectricmaterial layer is followed by the procedure of sintering the secondpiezoelectric material layer.

In accordance with certain embodiments of the method of forming a DSRspeaker element this includes the procedure of polishing fins.

In accordance with certain embodiments of the method of forming a DSRspeaker element the ratio of thickness of the flexure benders to thewidth of the gaps separating them from the rest of the layer is largerthan 2.

In accordance with an aspect of the invention, a DSR speaker element isprovided. The DSR speaker element includes: a moving element made from apiezoelectric material, and at least one flexure bender including a pairof electrodes and a portion of piezoelectric material. The flexurebender is connected to the moving element and configured to move themoving element in response to an electrical stimulus to the electrodesalong an axis perpendicular to the moving element surface. Thepiezoelectric material in the moving element and the portion ofpiezoelectric material in the flexure bender are made from a givenpiezoelectric material layer by the common deposition of thepiezoelectric material layer and the subsequent forming of gaps in thepiezoelectric material layer. The piezoelectric material layer issupported on a substrate having a cavity below the moving element. Thesubstrate also serves as a mechanical stopper that limits the movementof the moving element.

In accordance with certain embodiments the DSR speaker element includesa stopper disposed on the other side of the moving element. The stopperis configured to limit motion of the moving element.

In accordance with certain embodiments of the DSR speaker element, theflexure bender includes a second piezoelectric material layer disposedon the pair of electrodes and a third electrode disposed on the secondpiezoelectric material layer.

In accordance with certain embodiments of the DSR speaker element, thegaps are formed using disposing removable fins made from a material thatcan later be selectively removed on a sacrificial layer. The finsdefining the future gaps in piezoelectric material that will be addedlater.

In accordance with certain embodiments of the DSR speaker element,piezoelectric material is disposed over removable fins or over materialother than piezoelectric material that will later form a portion of themoving element, and said disposed piezoelectric material may be removedfrom said structures using polishing, chemical mechanical polishing, orother planarization techniques known in the art.

In accordance with certain embodiments of the DSR speaker element, oneof the electrodes is thicker than the other one of the electrodes andresists lateral shrinking.

In accordance with certain embodiments of the DSR speaker element, anarray of DSR speaker elements is provided.

In accordance with certain embodiments of the DSR speaker element, theratio of thickness of the flexure benders to the width of the gap islarger than 2.

In accordance with an aspect of the invention a method of forming apiezoelectric element is provided. The method includes the procedures ofpreparing a substrate base and disposing a first electrode layer on thesubstrate base. The first electrode layer is smaller than the surfacearea of the substrate base and is sized and designated for a specificfunction or purpose. The method also includes the procedure of disposinga thin piezoelectric material layer on the first electrode layer. Thedeposited thin piezoelectric material layer is not able to sustain orsupport itself without the support of the substrate. The method alsoincludes the procedure of disposing a second electrode layer on thepiezoelectric material layer. The second electrode layer is smaller thanthe surface area of the first thin piezoelectric material layer andthicker or thinner than the first electrode layer. The method alsoincludes the procedure of forming gaps through the piezoelectricmaterial layer to define a first functional section including a portionof electrode layers and piezoelectric material and a second functionalsection composed only substantially of piezoelectric material layer.

In accordance with certain embodiments of the method of forming apiezoelectric element, after the procedure of disposing a secondelectrode layer on the piezoelectric material layer there is theprocedure of disposing a second thin piezoelectric material layer on thesecond electrode layer.

In accordance with certain embodiments of the method of forming apiezoelectric element, after the procedure of disposing a second thinpiezoelectric material layer on the second electrode layer there is theprocedure of disposing a third electrode layer on the secondpiezoelectric material layer.

In accordance with certain embodiments of the method of forming apiezoelectric element, after the procedure of preparing a substrate baseand before the procedure of disposing a first electrode on the substratebase there is the procedure of disposing a sacrificial layer on thesubstrate base.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand the subject matter that is disclosedherein and to exemplify how it may be carried out in practice,embodiments will now be described, by way of non-limiting example only,with reference to the accompanying drawings, in which:

FIG. 1A is a schematic, top, perspective view of a piezoelectricactuated DSR speaker element, according to one embodiment;

FIG. 1B is a schematic top view of the top electrode layer of the DSRspeaker element of FIG. 1A;

FIG. 1C is a schematic top view of the middle electrode layer of the DSRspeaker element of FIG. 1A;

FIG. 1D is a schematic top view of the bottom electrode layer of the DSRspeaker element of FIG. 1A;

FIG. 1E is a schematic top view of the electrode layers of FIGS. 1B-1D,wherein at least part of the electrode layers are in alignment with eachother;

FIG. 1F is a schematic top perspective view of a portion of a DSRspeaker array that includes a plurality of the piezoelectric actuatedDSR speaker elements of FIG. 1A;

FIG. 1G is a schematic top view of a substrate that includes a pluralityof the DSR speaker arrays of FIG. 1F;

FIG. 2 is a schematic side, perspective view of a piezoelectric flexurebender with electrical connections;

FIG. 3 is a schematic side, cross-section view of an unfinished DSRspeaker element including fins, according to one embodiment;

FIG. 3A is a schematic side, cross-section view of an unfinished DSRspeaker element including fins, and a layer for the moving element whichis made of non-piezoelectric material, according to one embodiment;

FIG. 4 is a schematic side, cross-section view of the unfinished DSRspeaker element of FIG. 3 including electrode layers and piezoelectriclayers;

FIG. 4A is a schematic side, cross-section view of the unfinished DSRspeaker element of FIG. 3A including electrode layers, piezoelectriclayers and a mask layer;

FIG. 5 is a schematic side, cross-section view of the unfinished DSRspeaker element of FIG. 4 where the fins have been removed and the topelectrodes added;

FIG. 5A is a variant of the embodiment of FIG. 5 in which the differentelectrode layers are present above most of the surface of the substrate;

FIG. 5B is a schematic side, cross-section view of the unfinished DSRspeaker element of FIG. 4A wherein the fins have been removed and topelectrodes have been added, according to one embodiment;

FIG. 5C is similar to FIG. 5B but in this case, the different electrodelayers are present above most of the surface of the substrate;

FIG. 6 is a schematic side, cross-section view of an unfinished DSRspeaker element without fins, according to one embodiment;

FIG. 6A is a schematic side, cross-section view of an unfinished DSRspeaker element without fins and including a layer which does notcomprise piezoelectric material and which will be part of the centralmoving element, according to another embodiment;

FIG. 7 is a schematic side, cross-section view of the DSR speakerelement of FIG. 6 after the formation of gaps for defining differentfunctional sections;

FIG. 7A is a schematic side, cross-section view of the DSR speakerelement of FIG. 6A after the formation of gaps for defining differentfunctional sections and with moving element that is not made ofpiezoelectric material;

FIG. 8 is a side, cross-section view of an embodiment of a finished DSRspeaker element;

FIG. 8A is a schematic side, cross-section view of a finished DSRspeaker element, wherein the central moving element does not comprisepiezoelectric material, according to another embodiment;

FIG. 9 is a schematic side, cross-section view of a finished DSR speakerelement with two electrode layers, according to another embodiment;

FIG. 10 is a schematic top view of an electrode layer includingnon-functional metal portions, according to another embodiment;

FIG. 11 is a schematic side, cross-section view of an unfinished DSRspeaker element made using an electrode layer of FIG. 10;

FIGS. 11A and 11B are flow charts of an embodiment of a method offorming and producing a DSR speaker element for a DSR speaker;

FIG. 12 describes an alternative flow chart of another embodiment of amethod of manufacturing a DSR speaker element;

FIG. 13 is a schematic top view of an electrode layer of a DSR speakerelement, wherein the electrodes are split into sub-electrodes, andwherein the sub-electrode which is far from the electrical supply pointis fed using a thin metal trace;

FIG. 13A is a schematic cross section view of a flexure bender whichcomprises electrodes of FIG. 13;

FIG. 14 is a schematic top view of an electrode layer of a DSR speakerelement, wherein the electrodes are split into sub-electrodes, andwherein the sub-electrode which is far from the electrical supply pointis fed using at least one additional conductive layer;

FIG. 14A is a schematic cross section view of a flexure bender whichcomprises electrodes of FIG. 14;

FIG. 15 is a schematic top view of a piezo-electric actuator, comprisinga moving assembly;

FIG. 15A is a schematic cross section view of an assembly that can beused in the piezo-electric actuator of FIG. 15;

FIG. 15B is a schematic cross section view of another assembly that canbe used in the piezo-electric actuator of FIG. 15; and

FIG. 16 represents operation that can be performed to control thepiezo-electric actuator.

DETAILED DESCRIPTION OF EMBODIMENTS

Certain embodiments relate to a DSR speaker element (which can be alsodesignated as a sound pressure producing element or piezoelectric DSRspeaker element), comprising piezoelectric structures, and a method offorming thereof.

FIG. 1A is a schematic top, perspective view of an embodiment of a DSRspeaker element 1. A DSR speaker can typically comprise a plurality ofthese DSR speaker elements 1.

As shown in FIG. 1A, the DSR speaker element 1 comprises a centralmoving element 10. This central moving element 10 can be moved bypiezoelectric actuation.

In this embodiment, the DSR speaker element 1 comprises a firstfunctional section or portion comprising the central moving element 10,and a second distinct functional section or portion comprising aplurality of peripheral flexure benders 12. Although three peripheralflexure benders are shown in FIG. 1A, more than three peripheral flexurebenders can be used.

As shown, the DSR speaker element 1 can also comprise a surrounding area11.

According to some embodiments, the size (e.g. the diameter) of themoving element 10 is smaller than the shortest wavelength of the soundpressure pulse produced by the movement of the moving element 10.

According to some embodiments, the moving element 10 can be made assmall as practically possible. Indeed, the smaller the moving element10, the more moving elements 10 can be included in the same surface areato produce almost the same sound pressure level (SPL) with betterresolution.

In certain embodiments, a DSR speaker can comprise moving elements 10sized in the range of 50 μm-1000 μm (these values are however notlimitative), which is much smaller than the shortest wavelengthcontained in the sound pressure pulse that is produced.

According to some embodiments, the flexure benders 12 are connected at afirst end to the moving element 10 and at a second end to the area 11surrounding the moving element 10 and the flexure benders 12. Theflexure benders 12 are configured so that actuating the flexure benders12 causes the moving element 10 to travel along an axis (substantially)perpendicular to surface 11 (and also substantially perpendicular to amoving element surface).

According to some embodiments, the moving element 10, the flexurebenders 12, and the area 11 comprise piezoelectric material whichoriginates from at least one common piezoelectric material layer.

In the present specification, the expression “piezoelectric materiallayer” refers to a layer which comprises at least piezoelectricmaterial, or only piezoelectric material.

One non-limitative example of a suitable piezoelectric material is LeadZirconate Titanate (PZT). In certain embodiments, the thickness of thewhole piezoelectric material layer can be in the range of 2 μm-100 μm.

Gaps 14 in the piezoelectric material layer, on each side of the flexurebenders, define the distinct functional sections 10, 11 and 12. Gaps 16between the different flexure benders 12 define the peripheral portionof each flexure bender.

As mentioned, the flexure benders 12 comprise at least a piezoelectricmaterial layer (see e.g. references 21 or 22 in FIG. 2).

According to some embodiments, the flexure benders 12 further include afirst electrode layer 19, disposed below said piezoelectric materiallayer, and a second electrode layer 17 disposed above said piezoelectricmaterial layer.

According to some embodiments (see e.g. FIGS. 8 and 9), the flexurebenders 12 include a first electrode layer 19 disposed below a firstpiezoelectric material layer 21, a second (middle) electrode layer 17disposed above the first piezoelectric material layer 21, a secondpiezoelectric material layer 22 disposed above the second electrodelayer 17, and a third electrode layer 15 disposed above the secondpiezoelectric material layer 22. According to some embodiments, theelectrode layers 19, 17, 15, can comprise metal.

Each of the piezoelectric material layers 21, 22 can be a relativelythin layer, for example, in the range of 1-25 μm or 1.5-15 μm. Thesevalues are however non-limitative.

It should be noted that a flexure bender 12 with two piezoelectriclayers can get a bending with a larger amplitude for the same amount ofvoltage that would be applied to a flexure bender with a singlepiezoelectric layer. This allows flexure bender 12 to operate atrelatively low voltages.

Attention is now drawn to FIGS. 1B to 1D. Although these Figuresrepresent a configuration in which three electrode layers and twopiezoelectric material layers are used, it should be noted that eachflexure bender can also comprise only two electrode layers and a singlepiezoelectric material layer between them, or two electrode layers witha first piezoelectric material layer between the two electrode layersand a second piezoelectric material layer on the top electrode layer.

According to other embodiments, N electrodes layers (with N>3) and N−1(or N) piezoelectric material layers can be used. In this configuration,there can be alternatively an electrode layer and a piezoelectricmaterial layer.

As shown in FIGS. 1B to 1D, each of electrode layers 15, 17 and 19include flexure bender shaped electrodes 15F, 17F and 19F (in thisembodiment, three electrodes with a curved shape are depicted for eachelectrode layer) and conductive elements or lines 13 that are used tofeed electrical potentials to said electrodes.

As explained later in the specification (see e.g. FIGS. 13 and 14), therepresentation of the electrodes is schematic and according to someembodiments, at least part of the electrodes may be split into at leasttwo distinct sub-electrodes.

FIG. 1B is a schematic top view of top electrode layer 15. Top electrodelayer 15 includes flexure bender shaped electrodes 15F (in this casethree peripheral electrodes) and conductive lines 13A in a first patternor layout. At least one end of each electrode 15F is connected to theconductive lines 13A.

The electrodes 15F are separated one from the other by gaps 16, asalready mentioned with respect to FIG. 1.

FIG. 1C is a schematic top view of middle electrode layer 17. Middleelectrode layer 17 includes flexure bender shaped electrodes 17F (inthis case three peripheral electrodes) and conductive lines 13B in asecond pattern or layout different than the pattern of conductive lines13A.

At least one end of each electrode 17F is connected to the conductivelines 13B.

The electrodes 17F are separated one from the other by gaps 16, asalready mentioned with respect to FIG. 1.

FIG. 1D is a schematic top view of bottom electrode layer 19. Bottomelectrode layer 19 includes functional electrodes 19F (in this casethree peripheral electrodes) and conductive lines 13C in a third patternor layout different than the pattern of conductive lines 13A or 13B.Electrodes 19F are illustrated as flexure bender shaped, but othershapes and configurations are possible It should be noted that this alsoapplies to the electrodes of electrode layers 15 and 17.

Conductive lines 13A, 13B and 13C of the different electrode layers 15,17 and 19 have different patterns so that when at least part of theelectrode layers 15, 17 and 19 are in alignment in the DSR speakerelement 1 (in this case, each electrode of each electrode layer isaligned with the corresponding electrodes of the two other electrodelayers, as shown in FIG. 1E), the conductive lines 13A, 13B and 13C arenot in alignment. In particular, according to some embodiments, theoverlap of conductive lines 13A, 13B and 13C is reduced or minimized inorder to minimize parasitic capacitance.

FIG. 1E is a schematic top view of the electrode layers of FIGS. 1B-1D,wherein at least part of the electrode layers are in alignment with eachother. The piezoelectric material layers of FIG. 1A are not shown.Electrodes 15F, 17F and 19F of electrode layers 15, 17 and 19 are inalignment in the flexure area, the area designated for flexure benders12, whereas conductive lines 13A, 13B and 13C are configured to minimizeparasitic capacitance by having minimized overlap.

Referring back to FIG. 1A, flexure benders 12 can be configured so thatwhen an electric field is applied to electrode layers 15, 17 and 19,flexure benders 12 bend and move moving element 10 either upward ordownward along an axis perpendicular to surface 11. The direction thatflexure benders 12 move moving element 10 depends on the direction ofthe applied electric field. The amplitude that flexure benders 12 movemoving element 10 depends on a plurality of factors, for example one ofsuch factors being the amplitude of the applied electric field.

According to some embodiments, electrode layers 15, 17 and 19 in theflexure area of the element are connected in parallel so that flexurebenders 12 all work simultaneously.

When the DSR speaker element 1 is a part of an element array forming aDSR speaker, electrode layers 15, 17 and 19 of the DSR speaker elements1 on the same row or column may be connected in series via conductivelines 13 if passive matrix addressing is used. Passive Matrix addressingis discussed in detail in U.S. Patent Publication Number 2015/0071467,incorporated herein completely by reference (see e.g. paragraphs [0081]and [0098]). The DSR speaker element 1 can also include a substrate basewith a cavity and one or more stoppers described in detail below. Onecan also connect conductive lines 13 of one or more of the layers ofeach element directly to a voltage source.

Referring now to FIGS. 1F and 1G, a DSR speaker can include a pluralityof DSR speaker element 1 having moving elements 10 arranged in arrays135.

FIG. 1F is a top, perspective view of a portion of a DSR speaker array135 that includes a plurality of DSR speaker elements each comprising apiezoelectric actuated moving element 10.

In FIG. 1F, the majority of piezoelectric actuated moving elements 10are shown in their rest position 100, with moving elements 10 onsubstantially the same plane as area 11 surrounding moving elements 10.One actuated moving element 10AC is shown in an actuated position 110where actuated moving element 10AC is pushed away (in the upperdirection) from surface area 11. Actuated moving element 10AC is movedinto actuated position 110 by actuating flexure benders 12 of movingelement 10AC. In FIG. 1F, actuated position 110 is exaggerated in orderto clearly show and highlight the difference between a non-actuatedmoving element 10 and actuated moving element 10AC. Typically, themovement of actuated moving element 10AC in each direction is equal toor less than the sum of the thickness of the piezoelectric material andelectrode layers added together. This is however non limitative.

FIG. 1G is a schematic top view of a device that includes a plurality ofDSR speaker arrays 135 arranged on a substrate 31. In certainembodiments, substrate 31 may look either like a round silicon or glasswafer, or a sheet of silicon or glass. After manufacturing, the DSRspeaker arrays may be separated.

FIG. 2 is a side, perspective schematic view of a flexure bender 12. Forsake of clarity, it is shown as a rectangular unit. Flexure bender 12can include two piezoelectric material layers 21 and 22 and threeelectrodes of the three electrode layers 15, 17, 19. As alreadymentioned, different numbers of electrode layers and piezoelectricmaterial layers can be used.

According to some embodiments, the flexure bender 12 can comprise atleast one insulating layer and at least one additional conductive layer(e.g. in the case where the electrodes are split into sub-electrodes)and/or additional layers.

Piezoelectric layers 21, 22 are sandwiched between the electrodes of theelectrode layers 15, 17, 19. An electrode formed in the electrode layer19 is disposed below the piezoelectric layer 21, an electrode formed inthe electrode layer 15 is disposed on top of piezoelectric layer 22, andan electrode formed in the electrode layer 17 is disposed in betweenpiezoelectric layers 21 and 22.

Although FIG. 2 shows a configuration in which every layer totallycovers the layer disposed underneath, according to some embodiments, atleast part of the layers covers only part of the layer disposedunderneath.

When an electric potential is applied on electrode layers 15, 17 and 19,one piezoelectric layer 21 may contract while the other piezoelectriclayer 22 may expand, causing a side of flexure bender 12 to move from afirst, at rest position 23 downwards towards a second, down position 25.When the opposite potential is applied, one piezoelectric layer 21 mayexpand while the other piezoelectric layer 22 may contract, causing aside of flexure bender 12 to move upwards from a first, at rest position23 upwards towards a third, up position 24. The degree of movement ofside 23 of flexure bender 12 depends on a plurality of factors, such as(but not limited to): the piezoelectric materials used for piezoelectriclayers 21, 22, the layer thickness of piezoelectric layers 21, 22, thevoltage applied, the number of the sub-electrodes, their shape and theirstimulation scheme and the length of flexure bender 12.

Since the translation achieved from flexure bender 12 is larger whenflexure bender 12 is longer for a given electrical field, for a DSRspeaker application where one wants to move moving element 10 whilekeeping moving element 10 substantially flat and parallel to area 11surrounding moving element 10, flexure benders 12 can be designedaccording to some embodiments to be as long as possible in order toreduce the operation voltage. This is however not limitative.

In certain embodiments, relatively long flexure benders 12 are arrangedalong the perimeter of moving element 10. Due to mechanicalconsiderations, according to some embodiments, each flexure bender 12can be designed to be not much longer than a third of the perimeteraround moving element 10 (hence three flexure benders 12 are shown inFIGS. 1A and 1B), to avoid flexure benders 12 bending in the middlerather than pushing moving element 10 up or down. When flexure benders12 bend, thereby pushing moving element 10 up or down, moving element 10moves as one substantially flat surface without substantially bending ortilting (the moving element 10 remains substantially parallel to surfacearea 11).

Referring still to FIG. 2, electrical connections 26, 27 and 28 (whichcorrespond to the part of the conductive lines which extend from eachend of each electrode in FIGS. 1B-1D) can connect the electrodes of theelectrode layers 15, 17 and 19 to an external electrical component, suchas, a source of voltage (not shown). Electrical connection 28 isconnected to electrode layer 15, electrical connection 27 is connectedto electrode layer 17, and electrical connection 26 is connected toelectrode layer 19.

When flexure bender 12 is used as a bender actuator in a DSR speaker,electrical connections 26 and 28 can connect the electrodes of electrodelayers 15 and 19 to one of the voltage source's terminals, for example,the negative terminal. Electrical connection 27 can connect theelectrode of middle electrode 17 to the other terminal of the voltagesource, for example, the positive terminal. A voltage from the voltagesource will cause flexure bender 12 to bend.

When a flexure bender 12 is used as a bender sensor in a microphoneapplication, electrical connections 26 and 28 can connect the electrodesof electrode layers 15 and 19 to one terminal of an amplifier, andelectrical connection 27 can connect the electrode of middle electrodelayer 17 to the other terminal of the amplifier. When flexure bender 12is bent in either direction in response to pressure, for example, fromthe sound pressure waves, a small voltage will develop between electrodelayers 15, 17 and 19 that may be amplified by an amplifier.

FIGS. 3-7 illustrate an unfinished piezoelectric element (here after“unfinished sound pressure producing element” or “unfinished element”)at various stages during a process, in accordance with certainembodiments, for manufacturing piezoelectric elements, such as the DSRspeaker element 1 that was described in detail above. Verticaldimensions are exaggerated in order to highlight certain elements inportions of the Figures. In certain embodiments, the substrate may havea thickness of around 500 μm or other as determined by manufacturing andacoustic issues and the upper layers will have a total thickness closerto 3.5 μm. These values are however non limitative. The terms“disposed”, “deposited”, “disposing” and “depositing” can refer todirect disposing without any intermediate layers, or indirect disposingincluding an intermediate layer or intermediate layers.

FIG. 3 is a side, cross-section view of an unfinished DSR speakerelement 34 including fins 33. Unfinished element 34 includes a substrate31 onto which a sacrificial layer 32 is added.

In certain embodiments, substrate 31 can be silicon or glass wafers thatcan vary in diameter from 100 mm to 450 mm, or silicon or glass sheetsthat can be larger than 450 mm on the side. These values are however notlimitative.

Sacrificial layer 32 can be partially removed at a later stage in theprocess to create a space to allow a moving element 10 that will beadded later, the freedom to move away from substrate 31 (or towardssubstrate 31). The process of disposing sacrificial layer 32 cancomprise a step of disposing a layer of sacrificial material on eitherside of substrate base 31. Sacrificial layer 32 may be made from anyappropriate material, such as, silicon dioxide material, added or grownon to substrate base 31. Other materials can be used.

Unfinished element 34 also includes temporary fins 33, disposed on thesacrificial layer 32, or on the substrate 31.

Fins 33 can be made from a material (or from a plurality of materials)that can later be removed, for example, by chemical dissolving. Fins 33can be made of material that can be selectively removed later on withoutdamaging other layers, such as, piezoelectric material layers 21, 22,electrode layers 15, 17, and 19, or sacrificial layer 32. According tosome embodiments, the material(s) used for fins 33 may also be capableof withstanding relatively high temperatures appropriate for processingor sintering piezoelectric material or crystallizing piezoelectricmaterial. The material(s) from which fins 33 are constructed may bedifferent than the material of sacrificial layer 32. As an example, fins33 can be constructed from a layer of poly-silicon that is deposited ontop of sacrificial layer 32 and later defined by lithography processesto limit the layer of poly-silicon to the desired shape of the fins.

Fins 33 are constructed in a manner so that fins 33 can be removed at alater stage in the process to create gaps 14. According to someembodiments, the gaps 14 are created in piezoelectric layers 21, 22, anddefine the functional section of flexure benders 12. Thus, fins 33 canhave the same shape as the desired gaps 14 that are to be formed asshown e.g. in FIG. 1.

FIG. 3A shows yet another embodiment of an unfinished DSR speakerelement 36, which comprises fins 33 and sacrificial layer 32.

In this embodiment, a layer 35 which is used for constructing the movingelement portion does not comprise piezoelectric material. According tosome embodiments, the layer 35 that is used to construct the movingelement 35 is made of the same material as the fins 33.

This can result in a moving element with a smaller mass than one madefrom piezoelectric material that may be of high density and harder tomove at high frequencies.

FIG. 4 is a side, cross-section view of the unfinished element 34 ofFIG. 3 including electrode layers 17, 19 and piezoelectric layers 21, 22deposited on top of substrate 31.

Substrate 31 and sacrificial layer 32 (support and sustain thinpiezoelectric material layers 21, 22. The piezoelectric material layers21, 22 are also present on a central portion of the sacrificial layer 32

A first electrode layer 19, smaller than the surface area of substratebase 31, is patterned on top of sacrificial layer 32 in the flexureareas 37, the area designated for flexure benders 12.

Electrode layer 19 can also include conductive lines 13C to connect thedifferent electrodes 19F of the same layer to each other, and/or toneighboring elements and/or to a voltage supply point, to enablesimultaneous operation of flexure benders 12.

The formation of the electrode layer 19 can comprise depositing thematerial of the electrode layer 19 (such as metal) and then etching gapsin the metal to obtain the desired shape of the electrode layer 19 (thatis to say the different electrodes, the conductive lines and otherstructures in the electrode layer). In certain embodiments, electrodelayer 19 can be formed by depositing photo-resist material on portionswhere gaps in the metal are to be formed and then depositing metal toobtain the desired shape and then removing the photo resist material(“lift off”).

A first piezoelectric material layer 21 can be disposed on top ofelectrode layer 19. A second flexure bender shaped electrode layer 17,smaller than the surface area of substrate base 31, can be patterned ontop of first piezoelectric layer 21 in the flexure areas 37, the areadesignated for flexure benders 12, wherein at least part of the secondelectrode layer 17 is in alignment with the first electrode layer 19.

Electrode layer 17 can also include conductive lines 13B to connect thedifferent electrodes 17F of the same layer to each other and toneighboring elements and/or to a voltage supply point on the sameelement.

The electrode layer 17 can be formed using similar techniques as thetechniques described for electrode layer 19.

Conductive lines 13B and 13C can be configured to minimize parasiticcapacitance by having minimized overlap, as already explained withreference to FIG. 1E.

A second piezoelectric material layer 22 can be disposed on top ofsecond electrode layer 17. The second piezoelectric material layer 22can be a thin layer. According to some embodiments, the secondpiezoelectric material layer 22 is not deposited and there is only asingle piezoelectric material layer between the first electrode layer 19and the second electrode layer 17.

The construction of practical DSR speaker arrays 135 can require usingstacks of piezoelectric layers in the thickness range of 1-25 μm or1.5-15 μm.

Handling and transporting of thin films of piezoelectric material insuch a thickness range can be challenging since piezoelectric layersthat are that thin are very fragile, and are often unable to sustain orsupport their own weight, depending on the size of their height andlength.

It would be extremely difficult to first make thin piezoelectric sheetsin such a thickness range separate from substrate 31 and then transportand bond such piezoelectric sheets to substrate 31. Therefore,piezoelectric material can be first disposed on substrate 31 to formthin piezoelectric layers which are supported by substrate 31 andsacrificial layer 32, and then flexure benders 12 can be defined.

Substrate 31 can be made from a relatively stable material, and cancomprise, for example, silicon, glass or any other suitable materialused as a carrier material to support the piezoelectric material layersuntil the gaps 14 are formed that define the flexure benders and themoving element.

After the gaps 14 are formed, a portion of substrate 31 can be removedto create a cavity 800 (see e.g. FIG. 8) that may be required for theetch of the sacrificial layer 32 and/or the acoustic performance of theDSR speaker.

When using fins 33 on top of substrate 31, and if the piezoelectriclayers are constructed using pressing technology, one may use a buffermaterial when pressing the bottom piezoelectric layer 21 so as to avoiddamaging fins 33 during the pressing operation. This buffer material maybe in liquid form.

The depositing or forming of piezoelectric material layers 21, 22 can bedone using different methods known in the art such as sputtering,sol-get deposition, and pressing a fine powder (particle size less than2 μm) of the un-sintered piezoelectric material as is, or mixed with abinder. in some cases, these steps are followed by thermal treatment forsintering or recrystallization of the piezoelectric material. Thepiezoelectric material layers 21, 22 can be polarized between thecontact electrodes 15, 17, 19 by applying a potential between electrodes15, 17, 19 after the device manufacturing is completed.

Bottom piezoelectric layer 21 may be thermally treated before theaddition of thin conductive electrode layer 19. Alternatively, bottompiezoelectric material layer 21 can be thermally treated together withthin conductive electrode layer 19 after electrode layer 19 has beenadded. Further alternatively, bottom piezoelectric material layer 21 canbe thermally treated together with thin conductive electrode layer 19and the top piezoelectric material layer 22. After depositing conductiveelectrode layers 17, 19 and piezoelectric material layers 21, 22, beforeor after thermal treatment, the top surface of fins 33 can be polished.Polishing may be done to gain access to fins 33 material after othermaterial has been deposited on top of fins 33. Polishing can be followedby removal of fins 33 (for example, by the dissolving of the material offins 33) which leaves a piezoelectric material surface with gaps 14 thatdefine flexure benders 12. Fins 33 may be removed using removingprocesses such as, dry etch, wet etch, chemical dissolution, or anyother suitable process.

FIG. 4A is similar to FIG. 4, but shows the unfinished element 36 ofFIG. 3A. Similarly to what was described with respect to FIG. 4, a firstelectrode layer 41 (similar to electrode layer 19) can be deposited. Inthis case, the first electrode layer 41 is deposited and patterned asexplained above. A first piezoelectric material layer 43 can bedeposited on the first electrode layer 41, a second electrode layer 42can be deposited and patterned on the first piezoelectric material layer43, and a second piezoelectric material layer 44 can be deposited on thesecond electrode layer 42.

As already mentioned with respect to FIG. 4A, layer 35, which definesthe moving element, does not comprise piezoelectric material and can bemade of the same material as the fins 33.

In the embodiment of FIG. 4A, an additional mask 47 is disposed on thelayer 35 in order to protect this layer 35 when the fins 33 will beetched to create the gaps 14. Said mask 47 can be made from any suitablematerial used in photo lithography, and/or can also be a hard mask madeof metal, Silicon Dioxide, aluminum oxide or any other material that canresist the etching process of the fins 33.

FIG. 5 is a side, cross-section view of the unfinished element 34 ofFIG. 4 where fins 33 have been removed.

Removing fins 33 is done to define flexure benders 12 and moving element10 by forming gaps 14 between flexure benders 12, moving element 10, andsurrounding piezoelectric material 11. Unfinished element 34 of FIG. 5includes a third flexure bender shaped electrode layer 15, smaller thanthe area of substrate base 31, disposed on piezoelectric layer 22 in theflexure bender areas 37, wherein at least part of the third electrodelayer 15 is in alignment with at least part of first electrode layer 19and second electrode layer 17. Electrode layer 15 includes conductivelines 13A to connect the different electrodes 15F of the same layer toeach other and to neighboring elements and/or to a voltage supply pointon the same element. Electrode layer 15 can be disposed on piezoelectriclayer 22 either before or after the forming of gaps 14 (gaps 14 beingformed, for example, by removal of fins 33 which are the negative shapesof gaps 14). The patterning of electrode layer 15 can be done by similarmethods to those used to shape the electrode layers 17 and 19.

FIG. 5A is similar to FIG. 5 but in this case, the different electrodelayers are present on most of the surface.

The portions 41, 42, and 46 of the first, second and third electrodelayers are present in the flexure benders.

The portions 411, 412 and 521 of the first, second and third electrodelayers are present in the surrounding area 11, and the portions 500, 501and 502 of the first, second and third electrode layers are present inthe layer which will be part of the central moving portion 10.

As already mentioned, the portions 41, 42 and 46 are connected to anelectric potential. In this embodiment, the other portions 411, 421, 521and 500, 501, 502 are not connected to any electric potential. Theseother portions can make some processes easier to perform.

FIG. 5B is similar to FIG. 5 but in this embodiment, the moving elementis not made of piezoelectric material.

FIG. 5C is similar to FIG. 5B but in this case, the different electrodelayers portions are present above most of the surface of the element.

The portions 41, 42, and 46 of the first, second and third electrodelayers are present in the flexure benders.

The portions 411, 412 and 521 of the first, second and third electrodelayers are present in the surrounding area 11, and the portion 59 of thethird electrode layer is present on the layer 35 which will be part ofthe central moving portion 10.

As already mentioned, the portions 41, 42 and 46 are connected to anelectric potential. In this embodiment, the other portions 411, 421, 521and 59 are not connected to any potential and are left electricallyfloating. These other portions can be useful to ease some processing ofthe unfinished element of FIG. 5C.

FIG. 6 is a side, cross-section view of an unfinished element withoutfins, and FIG. 7 is a side, cross-section view of the unfinished speakerelement of FIG. 6 including gaps 14, according to an alternativeembodiment. In the embodiment of FIG. 6 and FIG. 7, gaps 14 that defineflexure benders 12 are created without fins by using alternative removaltechniques, for example: removing material using laser cutting,lithography, dry etch processes, wet etch processes, or other suitableprocesses. The forming of gaps 14 can be performed by the above listedtechniques either before or after the sintering of the piezoelectricmaterial. The gaps 14 can be formed by removing material in thepiezoelectric material layer (in this case layers 21 and 22), on eachside of a section comprising a portion of the first electrode layer, aportion of the first piezoelectric material layer, a portion of thesecond electrode layer and a portion of the second piezoelectricmaterial layer (if present, also a portion of the third electrodelayer).

The unfinished element of FIG. 7 is substantially the same as theunfinished element of FIG. 5. The forming of gaps 14 (which will allowdefining the flexure benders 12) can be performed by the above listedtechniques for example either before or after the sintering of thepiezoelectric material.

FIG. 6A is similar to FIG. 6 but in this embodiment, the layer 69, whichwill constitute the central moving element 10, does not comprisepiezoelectric material.

FIG. 7A represents the unfinished element 60 of FIG. 6A after theformation of gaps 70 on each side of a section comprising the firstelectrode layer 61, a portion of the first piezoelectric material layer63, the second electrode layer 62, a portion of the second piezoelectricmaterial layer 64, and the third electrode layer 65. The gaps 70 can beformed with at least one of the techniques mentioned with respect toFIG. 7.

FIG. 8 is a side, cross-section view of an embodiment of a DSR speakerelement 1.

The DSR speaker element 1 can comprise a moving element 10, flexurebenders 12 connected to the moving element 10, and a surroundingpiezoelectric material layer 11. Gaps 14 are present between the flexurebenders 12 and the moving element 10, and between the flexure benders 12and the surrounding piezoelectric material layer 11.

As shown in FIG. 8, a cavity 800 can be formed for the acousticperformance of the DSR speaker element 1.

Cavity 800 can be formed in the substrate base 31, at a first diameter80 smaller than the diameter of a portion comprising the moving element10 and flexure benders 12. Cavity 800 can also be used as an accessopening for etching a portion of sacrificial layer 32 at a seconddiameter larger than diameter 80.

Etching sacrificial layer 32 serves to create a first gap or space 81between the moving element 10 and the substrate base 31, in which themoving element 10 can move. As shown in FIG. 8, as sacrificial layer 32is etched, flexure benders 12 are undercut leaving first gap or space81, having a larger diameter than diameter 80 of first cavity 800, openbetween substrate 31 and flexure benders 12. Space 81 has a diameterthat is larger than the diameter of the moving element 10 and theflexure benders 12.

On one side of moving element 10, between moving element 10 andsubstrate 31, moving element 10 is able to move within space 81 bybending flexure benders 12 in a first direction towards substrate 31until moving element 10 reaches a surface 811 of substrate material 31.

The range of motion of moving element 10 is limited in the firstdirection by surface 811. Surface 811 can serve as a first stopper 811of the motion of moving element 10. On the other side of moving element10, moving element 10 is free to move. A second stopper 82 can be formedlimiting the movement of moving element 10 within a second space 86having a diameter larger than the diameter of the portion comprisingmoving element 10 and flexure benders 12.

According to some embodiments, the second stopper 82 has a radialportion 821 for stopping the motion of moving element 10, and an anchorportion 822 for anchoring the second stopper 82 to the surroundingpiezoelectric material layer stack 11.

Moving element 10 is able to move within space 86 by bending flexurebenders 12 in a second direction away from substrate 31 until movingelement 10 reaches the second stopper 82. Thus, the range of motion ofmoving element 10 is limited in the second direction by the secondstopper 82.

The range of motion of moving element 10 is thus limited by stoppers 82,811 on either side of moving element 10.

According to some embodiments, bottom stopper 811 and/or top stopper 82can be rigid. According to some embodiments, bottom stopper 811 and/ortop stopper 82 can facilitate acoustic performance, and enable passivematrix addressing.

According to some embodiments, top stopper 82 can be made using anelectroforming process on top of DSR speaker element 1.

According to some embodiments, top stopper 82 can be made by bondingpre-fabricated stoppers 82 with anchor portions 822 to DSR speakerelement 1.

When designing moving element 10 for an array 135 in order to make a DSRspeaker, other considerations may be taken into mind. According to someembodiments, the natural resonance frequency of moving element 10 andflexure benders 12 may correspond to the drive clock. In addition, gaps14 in the piezoelectric material layers that define piezoelectricflexure benders 12 from the rest of the layer stack area 11 may be smallenough so as to minimize acoustic short between the two sides of movingelement 10. According to some embodiments, the total translation ofmoving element 10 may be smaller than or equal to the total thickness ofthe layers that are part of flexure benders 12.

According to some embodiments, the ratio of thickness of flexure benders12 to the width of gap 14 is larger than 2. This value is however notlimitative.

According to some embodiments, the shape of one or more electrode layers15, 17 and 19 may be limited to the areas just below or overpiezoelectric layers 21, 22 making flexure benders 12 for actuation andnarrow conductive lines 13 to connect speaker element 1 as a part of aspeaker element array 135 required to construct a DSR speaker.

Using electrodes 15F, 17F and 19F of the required shape ensures bendingof only flexure benders 12 and not of moving element 10. The overlap ofconductive lines 13A, 13B, 13C may be minimized so as to reduce theparasitic capacitance. For this reason, it is better if conductive lines13A, 13B and 13C connecting the electrodes 15F, 17F and 19F of eachlayer 15, 17 and 19 have a minimal overlap. Also, this conductive linelayout ensures that the piezoelectric material polarization will takeplace almost only in the area of flexure benders 12 where polarizationpotential is created when applying voltage to these conductive lines 13.

Alignment structures (not shown) can be used to enable the alignment ofelements that are being deposited with previously deposited elementsthat have been buried by other layers.

For example, alignment structures can be used to align electrode layer17 with electrode layer 19 buried below piezoelectric material layer 21.In order to expose the alignment structures and enable precisealignment, windows can be opened in the layers (meaning a portion of theupper layers are removed) above the alignment structures in the generalarea of where the buried elements are located to expose the alignmentstructures for the alignment process. The alignment marks do not have tobe placed in the element area or in the DSR array but can reside in theopen areas between the arrays that are later used for cutting thefinished product into single DSR speaker arrays.

FIG. 8A is similar FIG. 8 but in this embodiment, the moving element 10does not comprise piezoelectric material.

FIG. 9 is a side, cross-section view of a DSR speaker element 2 with twoelectrode layers, according to another embodiment. The DSR speakerelement 2 comprises flexure benders 90 which comprise a singlepiezoelectric material layer 92 sandwiched between a first bottomelectrode layer 91 and a second top electrode layer 94. In certainembodiments, one of the electrode layers 91 or 94 may be thinner orthicker than the other electrode layer, and thick enough to resistlateral shrinking (that is to say thick enough to resist contraction andexpansion to enable flexure bender 90 to bend).

According to certain embodiments, a flexure bender that comprises twopiezoelectric layers, one expanding piezoelectric layer on top ofanother piezoelectric layer that contracts, will have a largertranslation per applied electrical field than a flexure bender 90 thatcomprises a single piezoelectric layer 92 on top of another supplementalmaterial or just a single piezoelectric layer 92 by itself.

In certain embodiments, conductive lines 13 or flexure bender shapedelectrodes can be defined by creating gaps in a continuous electrodelayer.

FIG. 10 is a schematic top view of an electrode layer includingnon-functional metal portions 500, according to another embodiment.

The electrode layer of FIG. 10 is similar to the electrode layers ofFIGS. 1B-1D, but in this embodiment, the electrode layer of FIG. 11includes non-functional metal portions 500.

Non-functional metal portions 500 may be a result of the manufacturingprocess used to make the electrode layer. For example, a layer of metalcan be disposed on a substrate and then electrodes and conductive lines13 may be formed or cut out from the metal sheet by etching gaps 41 inthe metal sheet. The cutting out of the electrodes and conductive lineswould result in non-functional metal portions 500 being disposed on thearea of the moving element 10 and the area 11 surrounding flexurebenders 12.

FIG. 11 is a schematic side, cross-section view of an unfinished DSRspeaker element made using an electrode layer of FIG. 10. The structureof FIG. 11 is substantially the same as the structure of FIGS. 5 and 7,except that the structure of FIG. 11 includes non-functional metalportions 500. The non-functional metal portions 500 are present in thecentral moving element and in the surrounding area.

Non-functional metal portions 500 will not be connected to any potentialand thus float in the piezoelectric material.

Reference is now made to FIGS. 11A and 11B, which describe a flow chartof an embodiment of a method of forming and producing a DSR speakerelement 1 for a DSR speaker. In embodiments of the presently disclosedsubject matter, fewer, more and/or different steps than those shown inFIGS. 11A and 11B may be executed.

In embodiments of the presently disclosed subject matter one or moresteps illustrated in FIGS. 11A and 11B may be executed in a differentorder and/or one or more groups of steps may be executed simultaneously.The method is suitable for forming a piezoelectric element that has aplurality of distinct functional sections or portions that are,according to some embodiments, initially formed from a common layer ofpiezoelectric material, wherein the functional sections or portions aremade distinct from one another by forming gaps in the common layer ofpiezoelectric material. However, the method will be discussed in thecontext of forming a DSR speaker element, such as DSR speaker element 1described above.

In addition, in the method of FIG. 11A, three electrode layers and twopiezoelectric layers are formed. However, this is not limitative and adifferent number of electrode layers and piezoelectric layers can beformed, as already mentioned for the various previous embodiments.

In step 202, a substrate base can be provided. With reference to FIG. 3,substrate base 31 is provided from an appropriate material, such assilicon or glass material.

In step 204, a sacrificial layer can be disposed on the substrate base.With reference to FIG. 3, sacrificial layer 32 which is prepared from anappropriate material, such as (but not limited to), silicon dioxidematerial, can be disposed on substrate base 31.

In step 206, removable and disposable fins can be disposed on thesacrificial layer, the fins defining future gaps in piezoelectricmaterial that will be added later.

According to some embodiments, fins are not disposed and the gaps can bemade later using removal techniques.

With reference to FIG. 3, fins 33 can be formed using an appropriatematerial, such as (but not limited to), poly-silicon material, and canbe disposed on sacrificial layer 32 in a pattern that will define gaps14. According to some embodiments, the fins 33 can be created bydisposing a layer of suitable material and defining fins 33 from thatlayer using lithography and etching processes.

In step 208, a first electrode layer that is smaller than the surfacearea of the substrate base is disposed on the sacrificial layer. Withreference to FIG. 4, electrode layer 19 is formed with the designatedpurpose of acting in flexure bender 12, and is disposed on sacrificiallayer 32. In certain embodiments electrode layer 19 can be formed bydepositing photo-resist material on portions of sacrificial layer 32where gaps in the metal are to be formed and then depositing metal ontop of the sacrificial layer 32. In other embodiments electrode layer 19can be formed by depositing metal on sacrificial layer 32 and thenetching gaps in the metal.

In step 210, a first piezoelectric material layer can be disposed on topof the first electrode layer and supported and sustained by thesubstrate base.

With reference to FIG. 4, a relatively thin piezoelectric layer 21, inthe range of 1-25 μm or 1.5-15 μm thick (these values being notlimitative), comprising an appropriate piezoelectric material, such asPZT, is disposed on electrode layer 19.

In step 212, a second, middle electrode layer (that is smaller than thesurface area of the substrate base) can be disposed on the firstpiezoelectric material layer. With reference to FIG. 4, electrode layer17 is disposed on piezoelectric material layer 21. According to someembodiments, gaps 14 and 16 are formed to define the electrodes 17F. Atleast the gaps 16 can be formed by “etching” or “lift off”.

In step 214, a second piezoelectric material layer can be disposed onthe middle electrode layer.

According to some embodiments, a portion of the first and secondpiezoelectric material layer which are disposed on the middle portion ofthe substrate or of the sacrificial layer will constitute the movingelement.

According to some embodiments, and as shown in FIG. 4, a relatively thinpiezoelectric layer 22, in the range of 1-25 μm or 1.5-15 μm andcomprising an appropriate piezoelectric material, such as PZT, can bedisposed on electrode layer 17.

In step 216, a third electrode layer 19 that is smaller than the surfacearea of the substrate base can be disposed on the second piezoelectricmaterial layer.

With reference to FIG. 5 (and FIG. 6), electrode layer 15, whichcomprises a flexure bender shaped electrode, since it is formed with thedesignated purpose of acting in flexure bender 12, is disposed onpiezoelectric material layer 22.

According to some embodiments, gaps 14 and 16 are formed to define theelectrodes 15F. At least the gaps 16 can be formed by “etching” or “liftoff”.

According to some embodiments, at least part of the first, second andthird electrode layers are formed so as to be in alignment. Inparticular, the electrodes of the different electrode layers can be inalignment, as shown e.g. in FIG. 1E.

In step 218, gaps can be formed to define a plurality of distinctfunctional sections or portions in the common layer or layers ofpiezoelectric material.

With reference to FIG. 1A and FIG. 5 (and FIG. 7), gaps 14 can be formedby removing fins 33 or by etching on each side of a section comprisingthe first, second and third electrode layers and a portion of the twopiezoelectric material layers to define flexure benders 12.

A gap 14 can be formed between a first side of flexure bender 12 and thecentral layer forming the moving element 10, and a gap 14 can be alsoformed between another side of flexure bender 12 and surrounding area11.

According to some embodiments, forming gaps 14 defines flexure benders12 having at least one piezoelectric material layer 21 or 22 sandwichedbetween at least two electrode layers 15, 19, and defines a flexurebender 12 section and a moving element 10 section comprising a portionof piezoelectric layer 21 or 22.

In step 220, a portion or section of the substrate base can be removedto gain access to the sacrificial layer, the substrate base formerlysupporting a portion of the piezoelectric layers. With reference to FIG.8, a portion or section of substrate base 31 is removed at a firstdiameter 80, thereby forming a cavity 800, to gain access to sacrificiallayer 32.

In step 222, a portion or section of the sacrificial layer can beremoved to form a space between the central moving element and thesubstrate base. With reference to FIG. 8, a portion or section ofsacrificial layer 32 can be removed at a second diameter larger than thefirst diameter 80 of cavity 800 to form a space 81 between a first sideof moving element 10 and substrate base 31 so that substrate base 31functions as a first stopper 811 to delimit the range of motion ofmoving element 10.

In step 224 (which is not necessarily performed), a second stopper canbe disposed or placed adjacent the other side of the central movingelement. With reference to FIG. 8, stopper 82 is disposed or placedadjacent the other side of moving element 10 thereby forming a space 86between moving element 10 and stopper 82. Second stopper 82 can beanchored to DSR speaker element 1 using an anchor 822. Second stopper 82delimits the range of motion of moving element 10 when flexure benders12 are actuated, the actuation done by providing electrical stimulationto piezoelectric layers 21, 22 via electrode layers 15, 17, 19.

FIG. 12 describes an alternative embodiment of a method of manufacturinga DSR speaker element 1.

The method can comprise a step 120 of providing a substrate base, and astep 121 of forming a sacrificial layer on the substrate base. Accordingto some embodiments, the sacrificial layer is not formed.

The method can further comprise a step 122 of disposing a moving elementlayer which does not comprise piezoelectric material layer on a middleportion of the sacrificial layer or of the substrate. In FIG. 3A, thiscan correspond to layer 35.

According to some embodiments, removable fins are disposed on thesacrificial layer or on the substrate (step 143).

The method can then comprise a step 124 of disposing electrode layersand piezoelectric material layers. The number of electrode layers andpiezoelectric material layers can be chosen depending on theapplication.

According to some embodiments, step 124 can comprise disposing a firstelectrode layer (see e.g. electrode layer 41 in FIG. 4A) on saidsacrificial layer, disposing a first piezoelectric material layer (seee.g. first piezoelectric material layer 43 in FIG. 4A) on at least partof said first electrode layer, and disposing a second electrode layer(see e.g. second electrode layer 42 in FIG. 4A) on said firstpiezoelectric material layer, wherein at least part of the first and thesecond electrode layers are in alignment. After or as part of thedeposition of the first electrode layer (respectively the secondelectrode layer), gaps (such as gaps 16) can be formed along theperimeter of each electrode layer to define the different peripheralelectrodes (such as by etching or lift off).

The method can then comprise a step 125 of forming gaps (such as gaps14) to define the central moving element (comprising a materialdifferent than piezoelectric material) and the flexure benders.

If fins have been disposed, fins can be removed. If the moving elementlayer comprises the same material as the fins, a mask can be used toavoid removing the moving element layer.

If fins are not present, gaps can be made on each side of the sectiondefining the flexure benders by using removal techniques (such as, butnot limited to, removing material using laser cutting, lithography, dryetch processes, or other suitable processes). The section defining theflexure benders can comprise e.g. a portion of the first electrodelayer, a portion of the first piezoelectric material layer and a portionof the second electrode layer. If a different number of piezoelectricmaterial layers or electrode layers is used, the section defining theflexure benders will comprise the corresponding number of piezoelectricmaterial layers and electrode layers.

The method can further comprise steps 220 to 224 as described withrespect to FIG. 11B, in order to manufacture the DSR speaker element.

FIG. 13 is a schematic top view of an electrode layer 130 of a DSRspeaker element (such as element 1). The electrode layer 130 can beeither e.g. the bottom electrode layer and/or the top electrode layer.

In this embodiment, each electrode of said electrode layer is split intotwo sub-electrodes (according to some embodiments, each electrode issplit into N sub-electrodes, with N>2). In addition, each sub-electrodecan be addressed with a different electrical potential.

As shown in FIG. 13, one of the sub-electrodes 133 is closer to theelectrical supply than the other sub-electrode 131. A thin metal traceplaced next to the closer electrode can be used to provide an electricalsupply to the other sub-electrode.

When using a scheme where each of the electrodes is split into at leasttwo sub-electrodes, in some geometries, if different potentials areapplied to each of the sub-electrodes, the movements of the movingelement 10 may have more translation in a direction normal to thesurface of the moving element than when using a single electrode layoutand the same potentials.

Electrical supply to the closer sub-electrode 131 can be facilitateddirectly using connection 132.

According to some embodiments, the split into a plurality ofsub-electrodes is used for the top electrode layer and for the bottomelectrode layer. In operation, the sub-electrode 131 of the bottomelectrode may be connected to an opposite potential to that of thecorresponding top electrode and sub-electrode 133 of the bottomelectrode may be connected to an opposite potential to that of thecorresponding top electrode. According the some embodiments, if a twopiezoelectric layers and three electrode layers scheme is used, themiddle electrode can be connected to ground potential.

FIG. 13A is a schematic cross section view of a flexure bender with theelectrodes described in FIG. 13.

The top far sub-electrode 1330, or 131 in the top view of FIG. 13, isconnected to an electrical supply via conductor 1350 that is connectedto the narrow trace 134 (which is not visible in this cross-section).

The closer sub-electrode 1310 is connected directly to the conductor1350 through connecting section 132 (which is not visible in thiscross-section).

In the embodiment depicted in FIG. 13A, there are two piezoelectricmaterial layers 1370 and 1380 and three electrode layers 1325, 1326 and1327. The top electrode layer 1325 and the bottom electrode layer 1326comprise electrodes which are split. The middle electrode layer 1327 isconnected to the ground and comprises a single electrode which is notsplit.

According to some embodiments, the top far sub-electrode 1330 isconnected to a positive potential, the middle electrode 1360 isconnected to ground, the bottom corresponding far sub-electrode 1331 isconnected the a negative potential, the top closer sub-electrode 1310 isconnected to a negative potential and the bottom corresponding closerhalf electrode 1311 is connected to a positive potential. Said potentialcan be reversed to actuate the flexure bender in the opposite direction.

FIG. 14 is a schematic top view of an embodiment of an electrode layerin which each of the electrodes is split into (at least) twosub-electrodes as in FIG. 13, but where electrical supply to thesub-electrode 144 far from the electrical supply is facilitated using anat least one additional conductive layer.

Since the narrow trace 134 can still affect the bending of thepiezoelectric material layer below it, it may be beneficial to bring theelectrical potentials to the electrode 144 which is far from theelectrical supply by using additional conductive layers with aninsulating layer between said conductive layers and the electrodes.Further explanations will be provided with reference to FIG. 14A.

The connection between the additional conductive layer that connects thesub-electrode 144 to its connecting conductor 147 is made through twovia hole openings 145 and 146 in the insulating layers. As before, theconnection of the closer sub-electrode 141 to the connective conductor142 can be done directly.

FIG. 14A is a schematic cross section view of an embodiment of a flexurebender 1400 which comprises a layout in compliance with the electrodelayout of FIG. 14. It is to be noted that a different number ofelectrode layers and/or piezoelectric material layers and/or sub and topconductive layers can be used, depending on the design.

In this example, the flexure bender 1400 comprises two piezoelectricmaterial layers 1401 and 1403, a top electrode 1430, a bottom electrode1431, both split into two sub-electrodes, and a middle electrode 1402which is not split into different sub-electrodes.

The top electrode 1430 is split into a sub-electrode 1405 (identical toelectrode 144 of FIG. 14) and a sub-electrode 1409 (which is closer tothe electrical supply and identical to electrode 141 of FIG. 14).

The sub-electrode 1409 is connected directly to a conductor (equivalentto the conductor 142 of FIG. 14, but which is not shown in FIG. 14A),and from this conductor to an outside conductor 1410.

The electrical supply to the sub-electrode 1405 can be made through atop conductive layer 1407. This conductive layer 1407 can beelectrically insulated by insulating layer 1404 (placed below theconductive layer 1407) from the sub-electrode 1409 and connected only tothe sub-electrode 1405 through a via hole 1406 in the insulating layer1404. The conductive layer 1407 can be electrically connected viaanother via hole 146 to a conductor 147, both not shown in this crosssection but visible in FIG. 14.

As shown in FIG. 14, the bottom electrode structure is symmetrical tothe top electrode structure. As already mentioned for the top electrode1430, the bottom electrode 1431 is split into a sub-electrode 1415 and asub-electrode 1419.

The sub-electrode 1415 is connected through via hole 1416 to the bottomconductive layer 1417, wherein the via hole 1416 goes through theinsulating layer 1414, and from it to the outside conductor 1413 throughanother via hole and another conductor, similar to via hole 146 andconductor 147 of the top electrode layer.

In the embodiments of FIGS. 13, 13A, 14 and 14A, if a singlepiezoelectric material layer is used, it is possible to use only the topelectrode and the bottom electrode without the middle electrode. In thiscase, according to some embodiments, opposite polarities can be used.

In a non-limitative example, the middle, non-split electrode 1402 isconnected to ground potential, the top sub-electrode 1405 can beconnected to a voltage of value +10V, the bottom sub-electrode 1415 canbe connected to a voltage of value −10V, the top sub-electrode 1409(which is closer to the electrical supply) can be connected to a voltageof value −10V and the bottom sub-electrode 1419 (which is closer to theelectrical supply) can be connected to a voltage of value +10V.

According to other embodiments, in which a single piezoelectric layerand two electrode layers are used, both bottom and top electrodes can besplit into at least two sub-electrodes.

In this case, the two sub-electrodes can be connected to oppositepotentials.

According to other embodiments, in which a single piezoelectric layerand two electrode layers are used, one of the electrodes, for example,the bottom electrode can be split into two sub-electrodes while theother electrode remains a whole electrode.

In this case, the two sub-electrodes can be connected to oppositepotentials while the whole electrode can be connected to the ground.

Other configurations can be used (number of sub-electrodes, number ofelectrode layers and piezoelectric layers, etc.).

Attention is drawn to FIG. 15, which is a schematic top view of anembodiment of a piezo-electric actuator 150.

As shown, the piezo-electric actuator 150 can comprise an assembly 151.

The assembly 151 can be attached or anchored to a base or body 155. Forexample, one side of the assembly 151 can be attached or anchored to thebody 155.

At least part of the assembly 151 can be in particular configured tomove in response to the application of an electrical stimulus. At leastpart of the assembly 151 can have a relative motion with respect to thebody 155.

According to some embodiments, at least part of the assembly 151 canmove either upwards or downwards along an axis perpendicular to asurface of the assembly 151, or along an axis perpendicular to the body155. In particular, the assembly 151 can bend upwards or downwards.

The cross-section (along a plane parallel to the body 155, orperpendicular to the motion of the assembly) of the assembly 151 canhave at least one straight side. For example, the cross-section can havea shape which is e.g. a square, a rectangle, etc. This is however notlimitative.

According to some embodiments, the assembly 151 has at least one sidewhich is not secured to the body 155.

According to some embodiments, the assembly 151 has at least three sideswhich are not secured to the body 155.

As shown in FIG. 15A, the assembly 151 can comprise a first electrode152, a second electrode 153, and at least one piezoelectric layer 154located between said first electrode 151 and said second electrode 153.

Assembly 151 can comprise also a substrate (not represented). Accordingto some embodiments, the substrate can be common to the assembly 151 andto the body 155.

Assembly 151 can be manufactured e.g. by depositing the required layersand forming one or more gaps between the assembly 151 and the body 155.

According to some embodiments, at least one of the first electrode 152and the second electrode 153 is split into at least two distinctsub-electrodes. In the example of FIG. 15A, the first electrode 152 isdivided into sub-electrodes 152 ₁, 152 ₂ and the second electrode 153 isalso divided into sub-electrodes 153 ₁, 153 ₂.

The first electrode 152 and the second electrode 153 can be connected toan electrical supply, using a plurality of conductive elements 159connected to the electrodes. Upon application of an electrical stimulus,the piezoelectric layer 154 can bend and the assembly 151 can moveupwards or downwards.

According to some embodiments, when a sub-electrode 152 ₁ of the firstelectrode is connected to a positive potential, and anothersub-electrode 152 ₂ of the first electrode is connected to a negativepotential, corresponding sub-electrodes 152 ₁, 152 ₃ of the secondelectrode are connected to opposite potentials with respect to thesub-electrodes 152 ₁, 152 ₂ of the first electrode. In some embodiments,the sub-electrode 152 ₁ is connected to a negative potential and theother sub-electrode 152 ₂ is connected to a positive potential, and thesub-electrodes of the second electrode 153 are connected to oppositepotentials.

According to some embodiments, the first electrode 152 and/or the secondelectrode 153 can be electrically fed as described with respect to FIG.13 and FIG. 13A. As described in these embodiments, electrical supply tothe sub-electrode closer to the electrical supply than the othersub-electrode is facilitated using an at least one thin metal traceplaced next to the closer electrode. Since these embodiments werealready described, they are not described again.

According to some embodiments, the first electrode 152 and/or the secondelectrode 153 can be electrically fed as described with respect to FIG.14 and FIG. 14A. As described in these embodiments, electrical supply tothe sub-electrode far from the electrical supply is facilitated using anat least one additional conductive layer. Since these embodiments werealready described, they are not described again.

According to some embodiments, the first electrode is connected to afirst conductive element, the second electrode is connected to a secondconductive element, and the first conductive element is not in alignmentwith the second conductive element.

According to some embodiments, assembly 151 can comprise at least threeelectrodes, and can be in compliance with any of the embodimentsdescribed with reference to FIGS. 13, 13A, 14 and 14A (these embodimentswere described for the flexure bender, but apply similarly to theassembly 151).

In particular, as illustrated in FIG. 16, the assembly 151 can comprise:

-   -   a first electrode 152, as described in FIG. 15A;    -   a first piezoelectric layer 157;    -   a middle electrode 156;    -   a second piezoelectric layer 158; and    -   a second electrode 153, as described in FIG. 15A.

This structure is similar to the structure described with reference toFIGS. 13, 13A, 14 and 14A.

As mentioned above, according to some embodiments, at least one of thefirst electrode and the second electrode can be split into twosub-electrodes.

According to some embodiments, the middle electrode 156 is not split.

According to some embodiments, the first electrode 152 and/or the secondelectrode 153 can be electrically fed as described with respect to FIG.13 and FIG. 13A. As described in these embodiments, electrical supply tothe sub-electrode closer to the electrical supply than the othersub-electrode is facilitated using an at least one thin metal traceplaced next to the closer electrode. Since these embodiments werealready described, they are not described again.

According to some embodiments, the first electrode 152 and/or the secondelectrode 153 can be electrically fed as described with respect to FIG.14 and FIG. 14A. As described in these embodiments, electrical supply tothe sub-electrode far from the electrical supply is facilitated using anat least one additional conductive layer. Since these embodiments werealready described, they are not described again.

According to some embodiments, an array comprising a plurality ofpiezo-electric actuators can be built, which can be interconnected usinge.g. conductive elements 159.

As shown in FIG. 16, an electrical stimulus (voltage) can be provided toat least one of the first and second electrodes (operation 160). Inparticular, if the first electrode 152 comprises two sub-electrodes,opposite electrical potentials can be applied to the sub-electrodes ofthe first electrode. Similarly, if the second electrode 153 comprisestwo sub-electrodes, opposite electrical potentials can be applied to thesub-electrodes of the second electrode. In some embodiments, and asmentioned above, if a sub-electrode of the first electrode receives anelectrical potential, an opposite sub-electrode of the second electrodereceives an opposite electrical potential.

The middle electrode 156 can be e.g. connected to the ground. Inresponse to the electrical stimulus, the assembly can move downwards orupwards (operation 161).

The present invention has been described with a certain degree ofparticularity, but those versed in the art will readily appreciate thatvarious alterations and modifications may be carried out.

It is to be noted that the various features described in the variousembodiments may be combined according to all possible technicalcombinations.

It is to be understood that the invention is not limited in itsapplication to the details set forth in the description contained hereinor illustrated in the drawings. The invention is capable of otherembodiments and of being practiced and carried out in various ways.Hence, it is to be understood that the phraseology and terminologyemployed herein are for the purpose of description and should not beregarded as limiting. As such, those skilled in the art will appreciatethat the concept upon which this disclosure is based may readily beutilized as a basis for designing other structures, methods, and systemsfor carrying out the several purposes of the presently disclosed subjectmatter.

Those skilled in the art will readily appreciate that variousmodifications and changes can be applied to the embodiments of theinvention as hereinbefore described without departing from its scope,defined in and by the appended claims.

The invention claimed is:
 1. A piezo-electric actuator comprising: anassembly comprising: a first electrode, a second electrode, and at leastone piezoelectric layer located between said first electrode and saidsecond electrode, wherein at least one of the first electrode and thesecond electrode is split into at least two different electricallymutually isolated sub-electrodes, called respectively a firstsub-electrode and a second sub-electrode, and wherein at least part ofthe assembly is configured to move upwards or downwards, in response toan electrical stimulus applied to at least one of said first and secondelectrodes, wherein, each of the two sub-electrodes is connected to anelectrical supply, wherein the piezo-electric actuator comprises aconductive layer connecting the electrical supply to the secondsub-electrode, wherein the conductive layer is insulated from the firstsub-electrode by an insulating layer, and wherein the conductive layeris electrically connected to the second sub-electrode through a via holepresent in the insulating layer.
 2. The piezo-electric actuator of claim1, wherein each of the first electrode and the second electrode is splitinto at least two different sub-electrodes.
 3. The piezo-electricactuator of claim 1, wherein a cross-section of the assembly has atleast one straight side.
 4. The piezo-electric actuator of claim 1,further comprising a base, said assembly being secured to said basealong at least part of one side of said assembly.
 5. The piezo-electricactuator of claim 2, wherein when the first sub-electrode of the firstelectrode is connected to a positive potential, and the secondsub-electrode of the first electrode is connected to a negativepotential, corresponding opposite first and second sub-electrodes of thesecond electrode are connected to opposite potentials with respect tothe first and second sub-electrodes of the first electrode.
 6. Thepiezo-electric actuator of claim 1, wherein: the first electrode isconnected to a first conductive element, the second electrode isconnected to a second conductive element, wherein the first conductiveelement is not in alignment with the second conductive element.
 7. Thepiezo-electric actuator of claim 1, comprising: a third electrode layer,a first piezoelectric layer located between said first electrode andsaid third electrode, and a second piezoelectric layer located betweensaid third electrode and said second electrode.
 8. The piezo-electricactuator of claim 1, wherein said first and second electrodes includeconductive elements for at least one of: the connection betweendifferent electrodes, the connection with another piezo-electricactuator, and the connection with an external electrical supply.
 9. Anarray of piezo-electric actuators comprising a plurality ofpiezo-electric actuators according to claim 1.